img=cv2.imread('G:\image\school1.png')
if img is not None and len(img. shape) ==3:
    print('img.shape:',img.shape)
    show_img('img',img,-1)
    if img.shape[2]==3:
        b,g,r=cv2.split(img)
        show_img('b',b,-1)
        show_img('g',g,-1)
        show_img('r',r,-1)
    elif img.shape[2] ==4:
        b,g,r,a=cv2.split(img)
        show_img('b',b,-1)
        show_img('g',g,-1)
        show_img('r',r,-1)
        show_img('a',a,-1)
